With remarkable development of information technology (IT), a great variety of portable information communication devices have been popularized. As a result, in the 21st century, we are moving toward a ubiquitous society in which high-quality information service is possible regardless of time and place.
Secondary batteries are very important to realize such a ubiquitous society. Specifically, secondary batteries, which can be charged and discharged, have been widely used as an energy source for wireless mobile devices. In addition, the secondary batteries have also been used as an energy source for electric vehicles and hybrid electric vehicles, which have been proposed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel.
As devices, to which the secondary batteries are applicable, are diversified as described above, the secondary batteries have also been diversified such that the secondary batteries can provide outputs and capacities suitable for devices to which the secondary batteries are applied. In addition, there is a strong need to reduce the size and weight of the secondary batteries.
Based on the shape of a battery case, the secondary batteries may be classified into a cylindrical battery having an electrode assembly mounted in a cylindrical metal can, a prismatic battery having an electrode assembly mounted in a prismatic metal can, and a pouch-shaped battery having an electrode assembly mounted in a pouch-shaped case made of an aluminum laminate sheet.
The electrode assembly mounted in the battery case functions as a power generating element, having a positive electrode/separator/negative electrode stack structure, which can be charged and discharged. The electrode assembly may be classified as a jelly-roll type electrode assembly configured to have a structure in which a long sheet type positive electrode and a long sheet type negative electrode, to which active materials are applied, are wound in a state in which a separator is disposed between the positive electrode and the negative electrode, a stacked type electrode assembly configured to have a structure in which a plurality of positive electrodes having a predetermined size and a plurality of negative electrodes having a predetermined size are sequentially stacked in a state in which separators are disposed respectively between the positive electrodes and the negative electrodes, or a stacked/folded type electrode assembly, which is a combination of the above two type electrode assemblies.
A general structure of a prismatic battery is shown in FIG. 1.
Referring to FIG. 1, a prismatic battery 50 is configured to have a structure in which a jelly-roll type electrode assembly 10 is mounted in a prismatic metal case 20, and a top cap 30, at which a protruding electrode terminal (for example, an negative electrode terminal) 32 is formed, is coupled to the open top of the case 20.
A negative electrode of the electrode assembly 10 is electrically connected to the lower end of the negative electrode terminal 32 on the top cap 30 via a negative electrode tab 12. The negative electrode terminal 32 is insulated from the top cap 30 by an insulating member 34. On the other hand, a positive electrode tab 14 of another electrode (e.g. a positive electrode) of the electrode assembly 10 is electrically connected to the top cap 30, which is made of a conductive material, such as aluminum or stainless steel, to constitute a positive electrode terminal.
In addition, in order to ensure electrical insulation between the electrode assembly 10 and the top cap 30 excluding the electrode tabs 12 and 14, a sheet type insulation member 40 is disposed between the prismatic case 20 and the electrode assembly 10, the top cap 30 is mounted to the case 20, and the top cap 30 and the case are coupled to each other by welding. Subsequently, an electrolyte is injected into the case 20 through an electrolyte injection port 43, the electrolyte injection port 43 is sealed by welding, and epoxy is applied to the welded portion. As a result, the battery is manufactured.
In recent years, however, a new type of battery cell has been required in accordance with a trend change for a slim type design or various other designs. Specifically, there is a high necessity for a battery cell configured to have a structure in which the battery cell can be efficiently mounted in a device even in a case in which the device does not have a sufficient space to receive the battery cell as a result of the reduction in size and thickness of the device.
Conventional devices are manufactured so as to have an approximately rectangular parallelepiped shape. In recent years, however, there have been developed devices having various external shapes. In a case in which a battery cell is configured to have a rectangular parallelepiped shape or a cylindrical shape, it is difficult to efficiently mount the battery cell in such devices having various external shapes.
For example, sides of a smart phone may be curved to improve grip. However, in a case in which a battery cell having a rectangular parallelepiped shape or a battery pack having a rectangular parallelepiped shape is mounted in a device designed so as to have such curved portions, space utilization of the device may be lowered.
That is, the curved portions of the device have dead spaces, in which the battery cell cannot be mounted. Ultimately, such dead spaces lower the capacity of the device per volume.
Therefore, there is a high necessity for a battery cell configured to have a structure in which the battery cell can be efficiently mounted in a device having various structures such that dead spaces are reduced, thereby maximizing the capacity of the battery cell.